This invention relates to wheel covers and, more particularly, to an improved retention means for removably fastening the wheel cover to an associated automotive wheel rim.
Wheel covers of both the one-piece and two-piece construction are well known in the art and have utilized retention means, as an integral part of the axially directed flange structure, which functions to bitingly engage the adjacent automotive wheel rim. Such wheel covers are exemplified in the U.S. patents to Lyon No. 2,624,634 and to Dagobert No. 3,317,249. In both of these patents, the retention means are provided generally at the free ends of a plurality of axially inwardly directed extensions of the axial flange. Such structure utilizes the relative resiliency of the extensions to cause the edges of retention teeth, provided at the radially outer edge of the extensions, to bitingly engage the associated wheel rim. This flexible biting engagement is necessary to secure the wheel cover to the wheel rim during the shocks and strains encountered in various driving conditions. Further, even under normal driving conditions the wheel cover flexes in response to flexing of the associated wheel as the wheel rotates. Accordingly, the retaining fingers must retain their biting engagement with the wheel rim even while the wheel cover flexes in response to rotation of the wheel. This engagement is necessary to prevent the wheel cover from becoming dislodged from the wheel rim and to prevent relative rotation between the wheel cover and the wheel rim.
The object of the teeth provided in these prior art wheel covers is to bite into the metal of the wheel rim to resist such relative rotation and axial movement of the wheel cover. For purposes of the present discussion, the penetration, or bite, of the tooth is dependent upon two factors. First, the bite is dependent on the force applied, and secondly, on the sharpness of the tooth. Accordingly, even if the force provided by the deflected extension is held constant, the penetration or bite would be increased by sharpening the teeth. Thus, to ensure meeting the requirements of standard industry torque and drop tests for the various types of wheel covers, it follows that by increasing the sharpness of the respective retention teeth, the desired retention characteristics would be enhanced. However, as the sharpness of the typically work-hardened retention element edges is increased, their susceptibility to damage due to axial forces on the wheel cover increases. Thus, the need exists for increasing the biting penetration of the retention teeth to achieve a greater overall holding power without sacrificing the axial force holding power.
These desired retention characteristics are attained by the present invention wherein there is provided an improved retention means for wheel covers and wherein each retention element includes at least one pair of retention teeth. Each pair is provided with a first relatively sharp tooth for biting engagement with the wheel rim and a second or relatively blunt stong tooth to resist axial displacement of the wheel cover and to otherwise provide support for its adjacent sharp tooth.